1. Field of the Invention
The present invention relates to methods for screening multi-layer electronic components. More particularly, the present invention relates to screening methods to check the quality of multi-layer ceramic electronic components, such as multi-layer ceramic capacitors.
2. Description of the Related Art
Recently, multi-layer ceramic electronic components, such as a multi-layer ceramic capacitor and a multi-layer piezoelectric component have been widely used. Each of the multi-layer electronic components is defined by a multi-layer ceramic element having ceramic layers and internal electrode layers alternately laminated, and includes external electrodes electrically connected to the internal-electrode layers. Such multi-layer ceramic electronic components are manufactured using thin-films and multi-layered configurations.
Particularly, to satisfy the demands of the market, multi-layer ceramic capacitors have increasingly been manufactured using increasingly thinner films and an increased number of layers of the multi-layer configuration.
However, in multi-layer ceramic capacitors, due to the thinner ceramic layers, small structural defects inside dielectric members decrease the reliability of the products. As a result, it is difficult to prevent defective products from being manufactured. Thus, a screening method is necessary to check the products and remove defective products.
The following are known conventional screening methods: (1) a method in which a DC voltage is applied with a fixed polarity to measure insulation resistance; (2) a method in which a DC voltage is applied with a reversed polarity to measure insulation resistance; (3) a method in which a DC voltage is applied while heating to measure insulation resistance; and (4) a method in which a DC voltage is applied and changes in a leakage current are observed to detect and remove defective products.
As shown above, a DC voltage is applied in each of the methods described above. Thus, in each method, only a DC voltage electric load is applied to the multi-layer ceramic capacitor to screen the product.
As a result, the conventional methods are not capable of detecting a multi-layer ceramic capacitor having inner-structural defects and a reduced useful life. Thus, when a defective condition occurs in the product, the life of the product is greatly reduced.
In addition, the above-described problems occur not only in the case of multi-layer ceramic capacitors, but also in other types of multi-layer ceramic electronic components.
To overcome the above-described problems with the prior art, preferred embodiments of the present invention provide a highly reliable method for screening a multi-layer ceramic electronic component, by which multi-layer ceramic electronic components having inner-structural defects and a reduced useful life are efficiently detected and removed.
According to a preferred embodiment of the present invention, a method for screening a multi-layer ceramic electronic component having internal electrodes laminated via a ceramic layer in a ceramic element includes the steps of applying an AC voltage to the multi-layer ceramic electronic component, applying a DC voltage to the multi-layer ceramic electronic component, and measuring an insulation-resistance value obtained when the DC voltage is applied to check the quality of the multi-layer ceramic electronic component.
When the AC voltage is applied to the multi-layer ceramic electronic component, with the load of the current applied to the multi-layer ceramic electronic component, the electrical resistance of the component is detected. In other words, in the actual use of the component in which an AC voltage is applied thereto, when the multi-layer ceramic electronic component has inner-structural defects and a reduced useful life, the method effectively detects such potential problems of the component.
As described above, after applying the AC voltage to the multi-layer ceramic electronic component, the DC voltage is applied and then, the insulation resistance value of the component obtained when the DC voltage is applied is measured to check the quality of the multi-layer ceramic electronic component. As a result, unlike the conventional method, the method in accordance with preferred embodiments of the present invention efficiently detects multi-layer ceramic electronic components having inner-structural defects a reduced useful life.
In the screening method in accordance with preferred embodiments of the present invention, the applied AC voltage is preferably in a range of about 40% to about 80% of a breakdown voltage.
When the AC voltage ranging from about 40% to about 80% of the breakdown voltage is applied, the potential defects of the multi-layer ceramic electronic component are effectively detected. Thus, this is an advantage of preferred embodiments of the present invention.
In the above case, the AC voltage is preferably in the range of about 40% to about 80% of the breakdown voltage. This is range is preferred because, when the applied AC voltage is less than about 40% of the breakdown voltage, the effects of inner-structural defects and reduced useful life are greatly reduced, thus greatly reducing the detection thereof. In contrast, when the AC voltage is larger than about 80% of the breakdown voltage, even non-defective products may break down.
Furthermore, in the screening method in accordance with preferred embodiments of the present invention, the AC voltage ranging from about 50% to about 70% of a breakdown voltage may be applied to the multi-layer ceramic electronic component.
By applying the AC voltage ranging from about 50% to about 70% of the breakdown voltage, without breaking down non-defective products, defects are even more efficiently and quickly detected. This is a further advantage of preferred embodiments of the present invention.
In addition, in the screening method in accordance with preferred embodiments of the present invention, the applied DC voltage is between approximately a rated voltage and approximately twice the rated voltage.
When the DC voltage is in the above-described range to measure an insulation resistance value obtained when the DC voltage is applied, defects, such as an insulation resistance defects, of the multi-layer ceramic electronic component are reliably and efficiently detected. Thus, preferred embodiments of the present invention provide a highly reliable screening method.
In addition, the multi-layer ceramic electronic component may be a multi-layer ceramic capacitor.
Among multi-layer ceramic electronic components, particularly, multi-layer ceramic capacitors have been manufactured with very thin films and an increased number of layers in the multi-layered configuration. As a result, defects, such as insulation failures, inner-structural defects, and reduced useful lives, are more likely to occur. However, with the screening method of preferred embodiments of the present invention, defective products are efficiently and reliable detected and removed. Thus, a highly reliable multi-layer ceramic capacitor is obtained using the method according to preferred embodiments of the present invention.
Other features, elements, characteristics and advantages of the present invention will become apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.